There is a 1.40T3 test build of the sdgtw probe that will allow you to transform any of the UIM alarm time fields into a time/date string and map the desired UIM alarm time field to the desired field in ServiceNow as long as the mapped field in ServiceNow accepts a character string (support for ServiceNow date/time format field is not supported). You would have to open a support case to get a copy of the 1.40T3 test build then add the following 2 key value pairs to the <setup> section of the sdgtw.cfg file from the probe's Raw Configure GUI:
convert_time_to_date_format = true
date_format = dd/MM/yy HH:mm:ss (this is the format used by default)